This proposal is submitted in response to PAR-03-056: NIA Pilot Research Grant Program, Research Objective #2: Cardiovascular and Cerebrovascular Aging: Behavioral, clinical, social, cellular, and molecular studies of cardiovascular and cerebrovascular aging. The PI (David J. Moser, Ph.D.) is in his first year of a career development award from NIA (1 K23 AG020649-01A1; "Aging, Vascular Disease and Cognition") and is conducting a longitudinal study on forearm blood vessel function and cognition in elderly patients with atherosclerosis. That ongoing study is based on preliminary data showing a strong relationship between forearm blood vessel function and cognition in these patients. For reasons discussed in detail in the body of this proposal, it is surmised that blood vessel function may serve as an indicator of total atherosclerotic risk factor burden and, because it is significantly associated with level of cognitive function, it is hypothesized that it will also be found to be associated with subsequent vascular-related cognitive decline. With additional research, this could eventually lead to the use of blood vessel function measures in the early identification of those individuals at greatest risk for vascular cognitive decline and dementia. What is lacking in the Prs current K23 project is a mechanism by which the relationship between forearm blood vessel function and cerebrovascular function can be explored. It is assumed that the relationship between forearm blood vessel function and cognition demonstrated by the preliminary data is the result of compromised cerebrovascular function but this has never been studied. If funded, the proposed pilot study will enable our research team to conduct PET imaging on 20 elderly subjects enrolled in the Prs K23 project, allowing for an unprecedented examination of the relationships among forearm blood flow, cerebral blood flow, cerebrovascular reserve, and cognition in the elderly. The proposed research is expected to yield publishable results and will also provide valuable pilot data for larger scale (e.g. R01) grant applications.